The California Supreme Court said Wednesday that it will hear a prosecution appeal of a ruling throwing out a state law that bans anyone who has been convicted of a violent felony from owning body armor.

The unanimous order was a victory for Attorney General Jerry Brown, who had asked the court to take up the case, and for San Francisco Police Chief George Gascón, who had urged Brown to appeal.

The law, passed in 1998, was intended to protect police against flak-jacketed criminals such as Lee Boutwell, who fatally shot San Francisco Officer James Guelff in November 1994 and wounded another officer before being killed in a shootout. Congress passed a similar federal law in 2002.

The state law makes it a crime, punishable by up to three years in prison, for felons with violent offenses on their record to possess or wear body armor. State regulations define body armor as apparel that provides "ballistic resistance to the penetration of the test ammunition" for certain types of guns, a standard also used to certify armor for police.

A state appeals court in Los Angeles ruled in December that the law was unconstitutional because its terms were so vague that the average person wouldn't know when he or she was violating it.

Even someone who owns an item that was sold as a bulletproof vest can't tell, without testing or expert advice, whether it fits the law's definition of body armor, the Second District Court of Appeal said in a 2-1 ruling, which overturned a Los Angeles man's conviction and prison sentence.

Gascón immediately denounced the ruling and called on Brown to appeal it. The attorney general usually appeals lower-court decisions that strike down state laws and did so in this case.

"Allowing criminals and gang members to arm themselves with body armor makes no sense, and I'm confident the Supreme Court will reverse this wrong-headed decision," Brown said Wednesday.